This invention relates generally to fuseholders for cartridge fuses, and, more particularly, to modular fuseholders for industrial control devices.
Historically, ferrule or cartridge-type fuses have been employed in open fuseholders and fuseblocks. The fuses are retained in fuse clips, and serve to protect load side equipment from damaging fault currents by opening a fuse link and breaking an electrical circuit through the fuse link between a power source or line side device or circuit and a load side power receiving device or circuit. Open fuseholders and fuseblocks, however, present a risk of electric shock by exposing energized metal surfaces of the fuse and the fuse block to inadvertent contact when the fuse is energized. Furthermore, a fuse puller is typically required to remove the fuses from the clips, and if a fuse puller is not available, attempts to remove the fuses with other tools such as screwdrivers and pliers may be made, thereby endangering a user and damaging the fuseholder or fuseblock.
Consequently, efforts have been made to improve the safety and convenience of cartridge fuses in use, and modular fuseholders have been developed with fuses and fuse clips enclosed in a protective housing to prevent accidental contact with exposed and energized metal surfaces of the fuse and fuseholder. Further, at least in some types of modular fuseholders, a drawer is used to house one or more fuses and the fuses are pulled from contact clips by opening the drawer, thereby eliminating use of tools to remove fuses from the clips. See, for example, U.S. Pat. No. 5,515,023. While these modular fuseholders have improved safety of cartridge fuses to trained users, hazardous conditions have been encountered in their use because they may be easily opened while the fuses are energized and under load, which can cause dangerous arcing to occur between the fuses and the contact clips. In addition, the drawer often is completely removable from the fuseholder body, thereby undesirably exposing energized metal portions of the fuseholder. Further, the fuse drawers are vulnerable to undesirable loading and operation with fuses of a different capacity, i.e., voltage and current rating, than for which the fuseholder was designed or intended to be used in a given application.
Moreover, at least some types of modular fuseholders, such as those used for industrial control devices, contain added features that are not always desired or necessary for certain applications. For example, some modular fuseholders designed to accommodate UL (Underwriters Laboratories) Class CC fuses and IEC (International Electrotechnical Commission) 10xc3x9738 fuses that are commonly used in industrial control devices include permanently mounted auxiliary contacts and associated rotary cams and switches to provide early-break and late-make voltage and current connections for motor control applications. However, these features increase costs and complicate assembly of the fuseholder. It would be desirable to provide a simpler, lower cost and more universally applicable fuseholder that could be easily upgraded to include added features on an as needed basis.
In an exemplary embodiment, a fuseholder includes a main housing configured for receiving a plurality of cartridge fuses, a fuse drawer configured for slidable insertion into the main housing, and a handle coupled to the drawer for opening the drawer to release fuses from the main housing. The fuse drawer is selectively positionable between an open position for loading and unloading of fuses, and a closed position wherein energized metal surfaces of the fuse and main housing are enclosed. The drawer handle is selectively positionable between an extended position and a retracted position relative to the drawer, and the handle is substantially flush with the drawer when in the retracted position. Therefore, the handle is not easily manipulated with one""s fingers when the fuse drawer is closed, thereby reducing a likelihood that the fuse drawer will be opened when the fuseholder is under voltage and current loads. Hazardous arcing conditions are thus avoided, and safety of the fuseholder is improved.
The drawer includes a handle recess adjacent the drawer, and the drawer handle may be released from its retracted position by prying the handle open with a tool, such as a flat blade screwdriver, inserted into the handle recess. The fuse drawer includes a drawer frame having a lock opening therethrough, and a lock member, such as a padlock is insertable into the lock opening to prevent closing of the fuse drawer as desired. Built in fuse rejection members are included in the main housing to prevent use of unacceptable fuses with the fuseholder, thereby further improving safety and facilitating proper use of the fuseholder.
The main housing further includes an auxiliary contact actuator that is selectively positionable between a first position and a second position in response to a position of the fuse drawer. A removable auxiliary contact cover provides access to the contact actuator, and a known switch assembly may be plugged into the main housing for actuation by the auxiliary contact actuator to upgrade the fuseholder to include advanced features, such as early-break and late-make voltage and current contacts. Thus, costly switching components are avoided in the fuseholder itself. A variety of terminal options, including screw terminals and spring terminals allow versatile wiring options in the field.
Therefore, a safer, lower cost, and versatile fuseholder is provided for efficiently providing fused connections for, for example, industrial control devices.